This invention relates to a machine and a method for the thermal treatment of liquid and semi-liquid food products, in particular, but without limiting the invention, for the thermal treatment (pasteurization) of products of the ice cream trade.
Thermal treatment machines of known type comprise a tank for containing the product to be subjected to the pasteurization treatment. Inside the tank there is a stirrer.
The containment tank is heated by a plurality of electrical heating elements to bring the product to the required treatment temperature.
One need felt by operators in the trade is the need to obtain a product of consistently high quality even when product composition or temperature is varied.
In particular, in machines of this kind, it is not uncommon for parts of the product nearest the walls of the tank to be burnt on account of non-optimal product heating.
Indeed, it is extremely difficult to control the local temperature of the heating elements to prevent the formation of hot spots.
Burning occurs locally mainly at the parts of the tank where the electrical heating elements are located and alters the organoleptic properties and hence the quality of the end product.
It is also known that the viscosity of the product tends to change as a function of temperature: thus, non-optimal product heating leads to incorrect or unwanted viscosity which in turn means that prior art pasteurizing machines may suffer from problems of insufficient stirring or, on the contrary, excessive fluidity resulting in the product spurting or splashing out of the tank.